塔克拉玛干沙漠南缘头状沙拐枣幼苗生长和生物量分配对不同灌溉量的响应

Influence of Irrigation Amounts on Seedling Growth and Biomass Allocation of Calligonum caput-medusae at the Southern Fringe of the Taklimakan Desert

水是荒漠生态系统中首要限制因子。由于水分限制程度不同,植物幼苗在生长过程中表现出不同的适应策略。在塔克拉玛干沙漠南缘的沙漠-绿洲过渡带,设计了0mm(处理A)、100mm(处理B)、200mm(处理C)3种不同的灌溉量,对头状沙拐枣幼苗生长和生物量分配展开实验性研究。结果表明:①处理A比处理B和处理C地下生物量均有所增加;不同灌溉条件下,头状沙拐枣幼苗的根冠比均小于1,随灌溉量的减少头状沙拐枣幼苗的根冠比从0.19增加到0.32;即头状沙拐枣通过改变根系生物量分配适应水分条件变化。②随灌溉量的减少,头状沙拐枣幼苗主根垂直深度和水平根幅均呈增加趋势。处理A时,头状沙拐枣幼苗根系深度达180cm以上,处理B和C的根系深度均低于160cm,表明头状沙拐枣幼苗通过根系的伸长生长来适应水分减少。③在生长过程中,头状沙拐枣通过老同化枝枯落适应土壤水分减少。④株高和冠幅随着灌溉量增加呈先增加后减小趋势,基径随着灌溉量的增加而增加,地上生长指标在不同处理间均无显著差异。

Water is a key limiting factor for desert ecosystem,and plant seedlings exhibit various adaptive strategies in different irrigation treatments.Our research on the effects of three irrigation treatments on the seedlings growth and biomass distribution of Calligonum caput-medusae was conducted at the southern fringe of the Taklimakan Desert,Northwest China.The three irrigation treatments were 0 mm（treatment 1）,100 mm（treatment 2） and 200 mm（treatment 3）,and the irrigation was applied once during the growing season.Changes in biomass allocation,root depth distribution,root surface area,root/shoot ratio,litter mass/aboveground mass rate were investigated.The root biomass of C.caput-medusae seedlings in treatment 1 is higher than in the other two treatments.Root/shoot ratio increases from 0.16 to 0.32 with decreasing irrigation treatments.The vertical length of main root and horizonal root range of C.caput-medusae seedlings is larger in treatment 1 than in the two other treatments.Root length in treatment 1 exceeds 180 cm,and that in the other two treatments is less than 160 cm.So C.caput-medusae adapts to soil water decreasing by increasing root length.Litter mass of C.caput-medusae seedlings increases with decrease of irrigation amounts.With increase of irrigation amounts,the plant height and crown width of C.caput-medusae seedlings increase at first and then decrease,and the basal stem increases continuously,but there is no significant difference among the three treatments.